so...
got 39 /40 vdc across the cr1
enough .. or find a bit more juice
6ca4 is very good so that is not the cause
Difference is left between left and right channel
Measure:
channel B 58 vdc
channel A 71 vdc
Meaning that volume knob now channel A is louder then channel B
not excactly the same volume of sound coming out of the speakers
Allready starting to rock and roll this thing now...also for pop music this thing is great.... have the tuner hang on to it an every station is very.. very nice Although my taste is cello..lute .. classical j.s. bach.. barockmusic, chambermusic....enjoy it today with a free/easy jazz station
got 39 /40 vdc across the cr1
enough .. or find a bit more juice
6ca4 is very good so that is not the cause
Difference is left between left and right channel
Measure:
channel B 58 vdc
channel A 71 vdc
Meaning that volume knob now channel A is louder then channel B
not excactly the same volume of sound coming out of the speakers
Allready starting to rock and roll this thing now...also for pop music this thing is great.... have the tuner hang on to it an every station is very.. very nice Although my taste is cello..lute .. classical j.s. bach.. barockmusic, chambermusic....enjoy it today with a free/easy jazz station
Hi Max29,
That sounds like it's working okay, leave it. The part appears to be working okay.
They don't sound too bad. Enjoy it! If you get a chance some day, try some 6922EH in there. There are other good tubes also, in the 6922 family. If they are National 6DJ8, you will like it better with other tubes.
-Chris
That sounds like it's working okay, leave it. The part appears to be working okay.
Those are the DC voltages on the plates of the 6DJ8's? That has little relation to volume level. For that you need to measure the AC voltage comming out with a mono tone in. The volume control does not track well at low levels. Don't be all freaked out about that.
They don't sound too bad. Enjoy it! If you get a chance some day, try some 6922EH in there. There are other good tubes also, in the 6922 family. If they are National 6DJ8, you will like it better with other tubes.
-Chris
chris Two points the pio cap feeding the 6ca4 is only 30 mfd is that enough ...big asc paper in oil on picture
Cannot leave the difference between left and right channel because l cause the left channel is behind in volume too much cannot hear hardly any music coming out when playing at low level Hear only channel A
The voltage is meased at different spots are
C 108 8 mfd w.cap Line .A C 110
C 8 8 mfd wondercap Line B C 10
Silver micas over R 08 --C108 ,, ,, R18-- C8
There are two pots ?? V .3 Line A --
V 103 Line B
here can i use them to get more bias ..into channel B 58 vdc
Do they need biassing as well maybe at ....- vdc
Cannot leave the difference between left and right channel because l cause the left channel is behind in volume too much cannot hear hardly any music coming out when playing at low level Hear only channel A
The voltage is meased at different spots are
C 108 8 mfd w.cap Line .A C 110
C 8 8 mfd wondercap Line B C 10
Silver micas over R 08 --C108 ,, ,, R18-- C8
There are two pots ?? V .3 Line A --
V 103 Line B
here can i use them to get more bias ..into channel B 58 vdc
Do they need biassing as well maybe at ....- vdc
cannot see where this to big a difference in vdc comes from
Need the schematics badly can i get/order a good copy....
See the volume is now only equal over both channels at say .. ±3 db
at...± 1 db hear only channel A
Think this is the last detail to be solved because this thing is a beauty allready now...cannot imagine after changing some of the old w.caps and wires and Rca´ s ...
So for my kind of music need not so much loudness but everything and detail at low and very low level of playing ..
At night it is handy as well to hear both channels at low db-level
Need the schematics badly can i get/order a good copy....
See the volume is now only equal over both channels at say .. ±3 db
at...± 1 db hear only channel A
Think this is the last detail to be solved because this thing is a beauty allready now...cannot imagine after changing some of the old w.caps and wires and Rca´ s ...
So for my kind of music need not so much loudness but everything and detail at low and very low level of playing ..
At night it is handy as well to hear both channels at low db-level
Hi Max29,
VR1 adjusts the bias on V1, VR2 on the second half of V1. VR2 on the output tubes (V2,V3).
They did tend to use much too high a capacitance off the rectifier tubes. I think Michael still does the same thing.
The problems with the darn manuals are that every small piece is on a different page. They end up being books even though the information is small.
To adjust the trim pots you need an audio generator and distortion meter.
So VR1 should be -1.1~0.0 V, VR2 should be -3.6~0.0 V, VR3 should be -1.2~0.0 V. These voltages are on the grids. As you can see the ranges are large and generally not too helpful.The phono section plates shuld be 36~62 V on the first, 45~145 V on the second. The output should have between 42 and 70 V on the plate.
-Chris
VR1 adjusts the bias on V1, VR2 on the second half of V1. VR2 on the output tubes (V2,V3).
They did tend to use much too high a capacitance off the rectifier tubes. I think Michael still does the same thing.
The problems with the darn manuals are that every small piece is on a different page. They end up being books even though the information is small.
To adjust the trim pots you need an audio generator and distortion meter.
So VR1 should be -1.1~0.0 V, VR2 should be -3.6~0.0 V, VR3 should be -1.2~0.0 V. These voltages are on the grids. As you can see the ranges are large and generally not too helpful.The phono section plates shuld be 36~62 V on the first, 45~145 V on the second. The output should have between 42 and 70 V on the plate.
-Chris
any other way to get vdc on both channels a bit closer together then
Thinking about....
Option.. place resistor (s) in the cicuit of channel with the 72 vdc...
Option .. get a diode in between 72 to the 58 channel
option ..place a pio...between both channels so current can move to and fro
Thinking about....
Option.. place resistor (s) in the cicuit of channel with the 72 vdc...
Option .. get a diode in between 72 to the 58 channel
option ..place a pio...between both channels so current can move to and fro
Hi Max29,
Do not expect the plate voltages to be equal in a tube amp, especially this one!
Let me say it again. The bias controls are set so that you have minimum distortion in each stage. The plate voltages will be different under these conditions. Understand that a dual triode is simply two tubes in one envelope. They have no matched characteristics, they are not the same. They are only the same brand. Therefore, do not expect anything like matched performance.
Any level differences are trimmed out by the ...... trimmer controls on the front panel. The DC plate voltages are not an indication of gain.
The alignment section of the manual is three pages and specifies the use of a Soundtech 1700, 1701 or equivalent (THD meter) along with a low distortion oscillator. You really need those things.
That is something the "tube rollers" do not understand. 🙄
Now, gain control non-linearity is something you can only improve by installing a super expensive volume control. M.E. should have installed a -20 dB mute with this unit (all pre's really).
-Chris
Do not expect the plate voltages to be equal in a tube amp, especially this one!
Let me say it again. The bias controls are set so that you have minimum distortion in each stage. The plate voltages will be different under these conditions. Understand that a dual triode is simply two tubes in one envelope. They have no matched characteristics, they are not the same. They are only the same brand. Therefore, do not expect anything like matched performance.
Any level differences are trimmed out by the ...... trimmer controls on the front panel. The DC plate voltages are not an indication of gain.
The alignment section of the manual is three pages and specifies the use of a Soundtech 1700, 1701 or equivalent (THD meter) along with a low distortion oscillator. You really need those things.
That is something the "tube rollers" do not understand. 🙄
Now, gain control non-linearity is something you can only improve by installing a super expensive volume control. M.E. should have installed a -20 dB mute with this unit (all pre's really).
-Chris
funny ...just thought about raising value resistor in front of trimmer control
and or lower the other one as weel
because now have trimmer control all the way up other one all the way down ....
but will change the e88cc as well because there seems to be a lot of difference between the two triodes inside an e88cc one breaks down very easily while the otherone is i
okee
Although better as the 6dj still prefer the 6922 eh
and or lower the other one as weel
because now have trimmer control all the way up other one all the way down ....
but will change the e88cc as well because there seems to be a lot of difference between the two triodes inside an e88cc one breaks down very easily while the otherone is i
okee
Although better as the 6dj still prefer the 6922 eh
funny because changing the two ecc left chanel to right channel ..
values lowers to 68 but the other one lowers to 54...
so no use at all
So it is no problem that there is vdc difference of 12 vdc to me because the tubes can handle that but need equal db
May be the wondercaps are emptying out as well on the channel B
Think channel B with his 68-is too high and the A is allright and relaxed
values lowers to 68 but the other one lowers to 54...
so no use at all
So it is no problem that there is vdc difference of 12 vdc to me because the tubes can handle that but need equal db
May be the wondercaps are emptying out as well on the channel B
Think channel B with his 68-is too high and the A is allright and relaxed
Hi Max29,
6DJ8's are built differently than 6922's. The 6922 structure is a frame that supports the grid much better than a 6DJ8. It is much less microphonic and has more consistant characteristics.
I would change them if I were you. Use the Euro equivalent to a 6922 in construction. That will be a special quality tube. Watch the heater current ratings are the same (some are higher).
You will need to align this unit, possibly in a shop, to ge the performance it is capable of. Alignment can make all the difference!
PM me.
-Chris
6DJ8's are built differently than 6922's. The 6922 structure is a frame that supports the grid much better than a 6DJ8. It is much less microphonic and has more consistant characteristics.
I would change them if I were you. Use the Euro equivalent to a 6922 in construction. That will be a special quality tube. Watch the heater current ratings are the same (some are higher).
You will need to align this unit, possibly in a shop, to ge the performance it is capable of. Alignment can make all the difference!
PM me.
-Chris
yes while working this so and little one realizes
on how crucial the 6922 is in this unit...
There is a guy selling 100pcs of them on ebay 600 $ you take 50
I 50 is that an idea ...
on how crucial the 6922 is in this unit...
There is a guy selling 100pcs of them on ebay 600 $ you take 50
I 50 is that an idea ...
Hi Max29,
😀
Yes.
And how much fun it was doing warranty. I almost lost my mind trying to get these to perform to spec and solve customer complaints. I finally convinced Counterpoint to use the Sovtek 6922 on the strength of microphonics alone.
You should try setting up an SA-1000 or SA-100 some time with the older 6DJ8's.
-Chris
😀
Yes.
And how much fun it was doing warranty. I almost lost my mind trying to get these to perform to spec and solve customer complaints. I finally convinced Counterpoint to use the Sovtek 6922 on the strength of microphonics alone.
You should try setting up an SA-1000 or SA-100 some time with the older 6DJ8's.
-Chris
chris... your are great
Having now philips e88cc in them.. the same... they are all different and on my tube tester the result seems reasonable
Took the ones with littlest difference between A and B section in them ..
Philips (only) good for shaving machines every body knows over here because many have worked there... dont tell
Having now philips e88cc in them.. the same... they are all different and on my tube tester the result seems reasonable
Took the ones with littlest difference between A and B section in them ..
Philips (only) good for shaving machines every body knows over here because many have worked there... dont tell
Hi Max29,
I just saw that we have cross posted! I don't need any tubes (I have enough).
-Chris
Edit: I was commenting on how important the tubes are in these, not to purchasing tubes.
I just saw that we have cross posted! I don't need any tubes (I have enough).
-Chris
Edit: I was commenting on how important the tubes are in these, not to purchasing tubes.
Hi Max29,
Morgan Jones has written a book called "Valve Amplifiers" that should explain a lot. Excellent book and highly recommended.
-Chris
There are a number of things that would be done differently. It would be another preamp entirely.
Morgan Jones has written a book called "Valve Amplifiers" that should explain a lot. Excellent book and highly recommended.
-Chris
Hi Max,
It's not cheap, but very worthwhile.
I am about to reread it.
Now, P M me. Click the email button right about
here
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|
V
It's not cheap, but very worthwhile.
I am about to reread it.
Now, P M me. Click the email button right about
here
|
|
V
Hi anatech,
You might want to try a different make than Sovtek for a 6922. From my THD measurements I found them to have a high third order harmonic. I also tried Philips and JJ, and found the JJ to be a better choice. I don't have the THD numbers at the moment but if your interested I'd be glad to post them.
You might want to try a different make than Sovtek for a 6922. From my THD measurements I found them to have a high third order harmonic. I also tried Philips and JJ, and found the JJ to be a better choice. I don't have the THD numbers at the moment but if your interested I'd be glad to post them.